Industrial robots are being used in industrial assembly operations in such numbers that their use is becoming common. Initially robots are being assigned to do monotonous mundane or hazardous tasks. For example, the automotive industry, which has the largest number of operating robots, are using them for jobs such as spot welding auto bodies and material handling. The accuracy and repeatability of the presently available robots is .+-.0.050 inches (.+-.1.25 mm) and is acceptable for tasks of these types. Assembly operations, such as hole preparation and fastener installation, require greater accuracy and repeatability than is now available in industrial robots and few robots have the capability to change the tools which it uses to perform the assembly tasks.
The speed at which robots move can allow a robot to perform many tasks simultaneously with the aid of a computer. In the aerospace industry the products, such as airframes, are characterized by low volume, high complexity assembly operations. The average military aircraft for instance has 450,000 fasteners which must be accurately installed during assembly in differet locations. Therefore, there has been a need to provide an interface system between the available industrial robots and the working tools which system can accommodate the inaccuracies of the robot and yet provide the desired accuracy, repeatability and speed to make use of the robot economic. At the same time, since in industries like the aerospace industry, many different operations may have to be performed simultaneously by a robot, the interface system must provide the capability to change tools as required.